Naval Research Sea Glider Applications

The beaked whale is the target of a new undersea glider trying to track the deep-diving mammals by their high-frequency clicks and squeals.

A Sea Glider unmanned underwater vehicle with an underwater microphone began patrolling the coast of Hawaii in late October and will finish up its initial mission in mid-November. By then, it will have collected half a terabyte of data.

By applying software that automatically picks up beaked whale sounds from the rest of the sounds of the ocean, the researchers hope to gain a deeper understanding of how these rare whales live.

The Sea Glider is one of a host of new acoustic tracking tools that are helping scientists better understand the behavior of deep sea whales. Using autonomous underwater gliders, hydrophones, and sophisticated algorithms, they are a key tool in the race to map where whales live.

The beaked whale appears to be particularly sensitive to the powerful sonar used by the world’s naval fleets. Over the past decade, dozens of these rare whales have died in a series of incidents that seem linked to naval exercises, even if it is hard to prove the connection.

The carcasses that wash up on shore are consistent with the hypothesis that the whales respond to the sonar by surfacing too quickly, inducing the bends. Nitrogen, and other gases that had been dissolved into the liquids inside their bodies by the high-pressure at depth, transform back into gas as the pressure is released. If they rise too fast, the amount of gas overwhelms the body’s natural systems for expelling it, causing bubbles to form in the bloodstream and tissues.

The U.S. Office of Naval Research, though, has been pouring money into learning more about the whales. This particular project received $1.5 million. The next step could be to integrate and calibrate their data with information from U.S. Navy hydrophone arrays.